A major obstacle to long-term control and cure of HIV has been the persistence of HIV in reservoirs that contain latently infected, resting, and productively infected CD4+ T cells. The recent cure of a patient with HIV by hematopoietic cell transplantation (HCT) with HIV-resistant cells has demonstrated the enormous potential of this strategy. Unfortunately, HIV-resistant donors are extremely rare, severely limiting this approach. Here we propose a multi-investigator program to study the biology of the HIV reservoir in patients and nonhuman primates, and to develop novel strategies to repopulate the hematopoietic system with HIV-resistant cells. We have assembled a team consisting of leaders in the fields of HIV, genetic modification, translational research, and transplantation. Specifically, we will combine autologous HCT with genetic modification approaches, allowing us to disrupt the CCR5 receptor in autologous stem cells, and also destroy the integrated HIV provirus contained within those cells. We propose 5 highly integrated projects in pursuit of our overall goal, and 5 cores for their support. Project 1, Hematopoietic Cell Transplant: Platform for Purging the Latent HIV Reservoir (Ann Woolfrey, FHCRC), will seek to clarify the relative contributions of the preparative regimen and the donor graft required for purging the latent HIV reservoir. Project 2, ZFN-Modified Stem Cells for HIV Eradication (Philip Gregory, Sangamo Biosciences), will seek to endow the transplant recipient's own cells with stable resistance to infection, via zinc finger nuclease disruption of the CCR5 locus. Project 3, CCR5 Targeting to Control HIV/SHIV in Nonhuman Primates (Hans-Peter Kiem, FHCRC), will use a non-human primate model of HIV/SHIV infection to determine whether genetic modification of the CCR5 locus and HCT can provide long-term control of HIV. Project 4, Targeted Disruption of Integrated SHIV by Engineered Homing Endonucleases, (Keith Jerome, FHCRC), will seek to directly address the problem of viral persistence, by designing highly specific homing endonucleases that can recognize and mutate integrated SHIV provirus in infected macaque hematopoietic cells. Project 5, Aptamer and Dendrimer Delivery of Zn Finger Nuclease and Homing Endonuclease mRNA and cDNA (John Rossi, Beckman Research Institute of the City of Hope), will develop and optimize delivery strategies by which ZFNs and HEs can be delivered to their target cells. Given our leading roles in Transplantation and HIV research, we believe we are uniquely positioned to move these concepts from a highly relevant nonhuman primate HIV/SHIV model toward a cure for HIV-infected patients. PUBLIC HEALTH RELEVANCE: The long-term goal of this project is to combine our expertise in hematopoietic cell transplantation with our unique zinc finger nuclease and homing endonuclease technologies to specifically target and modify 1) the CCR5 co-receptor for HIV, and 2) the integrated provirus itself. This comprehensive plan offers a plausible pathway toward a cure for individuals infected with HIV. Project 1 - Hematopoietic Cell Transplant: Platform for Purging the Latent HIV Reservoir Project Leader (PL): Ann E. Woolfrey (Description as provided by applicant): Hematopoietic cell transplant (HCT) has been reported to have purged the reservoir of latently HIV-infected cells in one patient who received an HIV-resistant graft. For this approach to become broadly feasible, it is imperative that we determine the factors involved in HCT that contribute to eradication of the reservoir. Project 1 aims to determine what components of HCT are critical for elimination of the latent viral reservoir. The broad aim of Project 1 is to develop a platform for delivery of HIV-resistant cells to replace latently infected cells. In order to accomplish this broad goal, it is imperative that we determine the role of the separate mechanisms that may contribute to long-term elimination of the reservoir: 1) intensive chemo/radiotherapy which may eradicate recipient lymphocytes and dendritic or antigen presenting cells;and 2) reconstitution of immunity with HIV-uninfected and HIV-resistant cells. We hypothesize that both dose-intensity and graft source contribute separately to elimination of latently infected cells. In Specific Aim 1, we will investigate in human subjects both 1) the dose-intensity of conditioning that produces a meaningful reduction in the quantity of latent viral infection, and 2) the role of the graft source in eliminating latently infected cells. In Specific Aim 2, the effect of a lymphoablative conditioning on latently SHIV infection will be studied carefully in a macaque model, so as to separate the role of conditioning from the role of the graft source. Finally, we hypothesize that, in the absence of HIV-resistant cells, the latent reservoir ultimately will be replenished over time by low level replication of virus. In Specific Aim 3, we will investigate the source of HIV responsible for replenishing the latent reservoir, by a phylogenetic analysis of viral sequences obtained from blood, cerebral spinal fluid, and the intestinal tract, before and after HCT. Result from Project 1 will be used together with that from Project 5 to develop a clinical protocol for delivery of genetically modified HIV resistant cells. Project 1 will rely heavily on Core A and Core B, for support of the primate experiments. The phylogenetic sequencing and analysis will be performed by Core C. PUBLIC HEALTH RELEVANCE: To date, only one successful cure for HIV has been reported, that of an HIV-infected patient given an allogeneic hematopoietic cell transplant (HCT) from a CCR5n32 homozygous donor. The objective of Project 1 is to investigate HCT as a method to purge the latent HIV reservoir. Ultimately knowledge gained from Project 1 will be used to develop a platform for transplantation of HIV-resistant cells.